Dendritic cells

Question 1

What are dendritic cells good for?

Answer 1

Best antigen presenting cell for activating and programming native T cells.

Question 2

What are the three main types of dendritic cells?

Answer 2

Conventional DCs
Plasmacytoid DCs-viral infections
Inflammatory DCs

Question 3

Properties of conventional DCs

Answer 3

Tissue resident-gut and lung.

Immature

Question 4

Properties of plasmacytoid DCs

Answer 4

• Sentinels for viral infections
• Secrete large amounts of class I interferon.
• Express intracellular PRR TLR7 and TLR9.
• Less effective at priming T cells.

Question 5

Properties of inflammatory DCs

Answer 5

• Recruited to tissues.
• Monocyte derived.
• Can also migrate to lymph node and activate T cells.

Question 6

Functions of intestinal DCs

Answer 6

• CD103 DCs in the gut are able to drive ‘tolerance’ to oral antigens from food and commensal bacteria.
• Induce the generation of regulatory T cells to promote tolerance to food/bacterial antigens.
• Dependent of TGFb and retinoic acid.

Question 7

Properties of tissue DCs

Answer 7

• Immature
• Have many dendrites which increase surface area for antigen capture.
• Low expression of costimulatory molecules.
• Express many chemokine receptors.
• Can take up particulate and soluble antigens by endocytosis.
• Have many endocytic vesicles containing MHCII and lysosomal proteins.

Question 8

Steps in pathogen induced licensing/ maturation.

Answer 8

Pattern recognition receptors license DCs to mature.

1. Dendritic cells capture Ag via phagocytic R
2. Activate response to pathogen through PRRs e.g. TLR
3. TLR signalling alters DC chemokine R expression. Induces CCR7- the receptor for CCL21- only happens when mature.
4. DCs can move via lymph to lymph nodes- DCs are mature.

Question 9

Properties of mature DCs

Answer 9

• High levels of costimulatory molecules e.g. CD80, CD86.
• Stop taking antigens up- poorly endocytic
• High levels of long lived MHC
• Attract naive T cells- express high levels of adhesion molecules, secrete CCL18.

Question 10

What is the process of priming in the activation of T cells and what is the overall process?

Answer 10

• Mature DCs present antigen to naive T lymphocytes= priming.
• Activate any antigen specific T cells to divide into effector cells that enter circulation.

Question 11

What factors alter the type of immune response generated?

Answer 11

Signals received during antigen uptake, maturation, T cell priming.

• The form of Ag e.g pathogen associated or apoptotic body.
• Tissue factors e.g inflammatory cytokines or damaged cell.

Question 12

What are the three types of antigen presenting cells?

Answer 12

Macrophages, B-cells, dendritic cells